On the secrecy performance of land mobile satellite communication systems

In this paper, we investigate the secrecy performance against eavesdropping of a land mobile satellite (LMS) system, where the satellite employs the spot beam technique, and both the terrestrial user and eavesdropper are equipped with multiple antennas and utilize maximal ratio combining (MRC) to receive the confidential message. Specifically, in terms of the availability of the eavesdropper’s CSI at the satellite, we consider both passive (Scenario I) and active (Scenario II) eavesdropping. For Scenario I where the eavesdropper’s channel state information (CSI) is unknown to the satellite, closed-form expressions for the probability of non-zero secrecy capacity and secrecy outage probability are derived. Furthermore, expressions for the asymptotic secrecy outage probability are also presented to reveal the secrecy diversity order and array gain of the considered system. For Scenario II where the eavesdropper’s CSI is available at the satellite, novel expressions for the exact and asymptotic average secrecy capacity are obtained. Based on a simple asymptotic formula, we can characterize the high signalto- noise ratio (SNR) slope and high SNR power offset of the LMS systems. Finally, simulations are provided to validate our theoretical analysis and show the effect of different parameters on the system performance

Distribution Characteristics of Phosphorus in the Sediments and Overlying Water of Poyang Lake

<div><p>Phosphorus (P) is a key indicator of the aquatic organism growth and eutrophication in lakes. The distribution and speciation of P and its release characteristics from sediments were investigated by analyzing sediment and water samples collected during high flow and low flow periods. Results showed that the average concentrations (ranges) of total phosphorus (TP) in the surface and deep water were 0.06 mg L^-1 (0.03–0.13 mg L^-1) and 0.15 mg L^-1 (0.06–0.33 mg L^-1), respectively, while the average concentration (range) of TP in sediments was 709.17 mg kg^-1 (544.76–932.11 mg kg^-1). The concentrations of TP and different forms of P varied spatially in the surface sediments, displaying a decreasing trend from south to north. P also varied topographically from estuarine areas to lake areas. The vertical distribution of TP and different forms of P were observed to decrease as depth increased. The P concentrations during the low flow period were higher than those during the high flow period. Inorganic phosphorus (IP) was the dominant form of P, accounting for 61%–82% of TP. The concentration of bioavailable phosphorus in sediments was relatively large, indicating a high risk of release to overlying water. The simulation experiment of P release from sediments showed that the release was relatively fast in the first 0-5 min and then decreased to a plateau after 1 hr. Approximately 84–89% of the maximum amount of P was released during the first hour.</p></div

Release kinetic curve of P in the surface sediments of Poyang Lake.

<p>Release kinetic curve of P in the surface sediments of Poyang Lake.</p

Vertical distribution of P fractions in sediment cores of Poyang Lake.

<p>Vertical distribution of P fractions in sediment cores of Poyang Lake.</p

The percentage of P fractions in sediment cores of Poyang Lake.

<p>The percentage of P fractions in sediment cores of Poyang Lake.</p

Side-Arm Control in Phosphine-Sulfonate Palladium- and Nickel-Catalyzed Ethylene Polymerization and Copolymerization

A series of phosphine-sulfonate ligands bearing various side-arm substituents were designed and prepared. The corresponding Pd­(II) complexes [κ²-(<i>P</i>,<i>O</i>)-2-(<i>P</i>PhAr)-1-benzenesulfonato]­Pd­(Me)­(dmso) (<b>Pd1</b>, Ar = <i>o</i>-MeO-C₆H₄; <b>Pd2</b>, Ar = <i>o</i>-PhO-C₆H₄; <b>Pd3</b>, Ar = <i>o</i>-(2,6-Me₂-C₆H₃)­O-C₆H₄; <b>Pd4</b>, Ar = <i>o</i>-PhSO₂-C₆H₄) and Ni­(II) complexes [κ²-(<i>P</i>,<i>O</i>)-2-(<i>P</i>PhAr)-1-benzenesulfonato]­NiPh­(PPh₃) (<b>Ni1</b>, Ar = <i>o</i>-MeO-C₆H₄; <b>Ni2</b>, Ar = <i>o</i>-PhO-C₆H₄; <b>Ni3</b>, Ar = <i>o</i>-(2,6-Me₂-C₆H₃)­O-C₆H₄; <b>Ni4</b>, Ar = <i>o</i>-PhSO₂-C₆H₄) were prepared and applied in ethylene polymerization and ethylene–polar monomer copolymerization. Catalysts <b>Pd2</b>, <b>Pd3</b>, <b>Ni2</b>, and <b>Ni3</b> are moderately active in ethylene polymerization (activity up to 8.7 × 10⁵ g mol^–1 h^–1), generating polyethylene with high molecular weights (<i>M</i>_n up to 105100) and high melting temperatures (<i>T</i>_m up to 131.6 °C). The two palladium catalysts can also initiate efficient copolymerization of ethylene with methyl acrylate, allyl cyanide, and allyl acetate. Most importantly, high copolymer molecular weights (<i>M</i>_n between 21600 and 82500) and high polar monomer incorporation ratios (between 6.1% and 15.2%) could be achieved simultaneously in this system. This side-arm strategy is highly effective in modulating the properties of the phosphine-sulfonate palladium and nickel catalysts

Concentrations of P fractions in sediments in high flow and low flow periods.

<p>Concentrations of P fractions in sediments in high flow and low flow periods.</p

Pearson's correlations between TP and P fractions in the surface sediments (n = 27, p<0.05).

<p>Pearson's correlations between TP and P fractions in the surface sediments (n = 27, p<0.05).</p

Spatial distributions of TP in the Poyang Lake.

<p>Spatial distributions of TP in the Poyang Lake.</p

Anomalous Λ‑Doubling in the Infrared Spectrum of the Hydroxyl Radical in Helium Nanodroplets

The X²Π_3/2 hydroxyl (OH) radical has been isolated in superfluid ⁴He nanodroplets and probed with infrared laser depletion spectroscopy. From an analysis of the Stark spectrum of the <i>Q</i>(3/2) transition, the Λ-doublet splittings are determined to be 0.198(3) and 0.369(2) cm^–1 in the ground and first excited vibrational states, respectively. These splittings are 3.6 and 7.2 times larger than their respective gas phase values. A factor of 1.6 increase in the <i>Q</i>(1/2) Λ-doublet splitting was previously reported for the He solvated X²Π_1/2 NO radical [von Haeften, K.; Metzelthin, A.; Rudolph, S.; Staemmler, V.; Havenith, M. <i>Phys. Rev. Lett.</i> <b>2005</b>, <i>95</i>, 215301]. A simple model is presented that reproduces the observed Λ-doublet splittings in He-solvated OH and NO. The model assumes a realistic parity dependence of the rotor’s effective moment of inertia and predicts a factor of 3.6 increase in the OH ground state (<i>J</i> = 3/2) Λ-doubling when the <i>B</i>₀^<i>e</i> and <i>B</i>₀^<i>f</i> rotational constants differ by less than one percent